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Combinations Calculator

Our Combinations Calculator helps you quickly find the number of ways to choose a specific number of items from a larger set, where the order of selection doesn't matter. It's perfect for probability problems, statistics, and understanding how many unique groups you can form.

Enter the total count of items you have to choose from.

Enter how many items you want to select from the total.

How it works

Our Combinations Calculator helps you quickly find the number of ways to choose a specific number of items from a larger set, where the order of selection doesn't matter. It's perfect for probability problems, statistics, and understanding how many unique groups you can form.


The Formula
The formula for combinations is: C(n, k) = n! / (k! * (n-k)!) Where:
• n is the total number of items available. • k is the number of items to choose from the set. • '!' denotes the factorial (e.g., 5! = 5 × 4 × 3 × 2 × 1).

Worked Example
  1. Example: Choosing Lottery Numbers

    Imagine a lottery where you need to pick 6 numbers from a pool of 49. The order in which you pick them doesn't matter; only the final set of 6 numbers counts. Using the combinations formula: n = 49 (total numbers) k = 6 (numbers to choose) C(49, 6) = 49! / (6! * (49-6)!) = 49! / (6! * 43!) = 13,983,816 There are 13,983,816 possible combinations of 6 numbers you could choose from 49.


Tips, Assumptions & Limitations
  • Remember, combinations are about selecting groups where order doesn't matter. If order matters, you need a permutation.
  • Factorials (n!) can grow very large quickly. This calculator handles large numbers for you.
  • The number of items to choose (k) cannot be greater than the total number of items (n).
FAQ

A combination is a way of selecting items from a larger group where the order of selection does not matter. For example, choosing apples A, B, and C is the same combination as choosing B, C, and A.

The key difference is order. In combinations, the order of items doesn't matter (e.g., {A, B} is the same as {B, A}). In permutations, the order does matter (e.g., (A, B) is different from (B, A)). Permutations count ordered arrangements, while combinations count unordered selections.

You'd use it for problems like: calculating lottery odds (where the order of numbers drawn doesn't matter), determining how many different teams can be formed from a group of players, or finding the number of ways to select a committee from a larger pool of candidates.

Companion article

Combinations Calculator: Understand How to Count Groups

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